Move Big Blue Button docs to tools, add to index

tools/big-blue-button.md

@@ -0,0 +1,14 @@
+# BigBlueButton
+
+[BigBlueButton](https://docs.bigbluebutton.org/)
+
+To mute with keyboard:
+
+options menu (three vertical dots in the upper right hand corner).
+
+`Alt + Shift + M`
+
+
+```{note}
+  There's an [issue to float mute/unmute](https://github.com/bigbluebutton/bigbluebutton/issues/9947) which will be helpful when screensharing; until then using the shortcut is crucial.
+```